1. Field of the Invention
This invention relates to a flask-type container made from plastic/synthetic material.
2. Prior Art
This type of container is already known for products which are discharged by creasing and/or squeezing the container. The containers are made from a compact plastic, usually from polyolefin having a density of 0.9 to 0.97 g/cm.sup.3. In an effort to reduce the material used in packaging, experiments have been conducted by reducing the mantle thickness, the mantle being the side wall of the body portion of the container. Reduction of material used in production of packaging has a significant ecological purpose today. Reducing the material used is both ecologically friendly and generally advantageous economically.
The packaging must be recycled. The cost of recycling may be determined based on the weight of the material used. The cost of recycling plastic packaging is very high. In Germany for example, the cost of recycling is even higher than the cost of the packaging material itself. Efforts to reduce the material used mainly in packaging are still limited.
For example, a 250 ml flask may be produced by an optimum process by using under 20 g polypropylene as a weight limit. The flask's mantle has a thickness of around 0.7 mm. An experiment using 15 g of polypropylene has also been performed. The result shows that the wall thickness of the flask's mantle is 0.5 mm. This method and other similar methods of reducing the wall thickness lead to the conclusion that when the flask is used, namely when the product is about to be discharged from the flask, the flask undergoes a cracking effect due to the instability of the flask's mantle. The flask's abilities to crease and recover are adversely changed due to instability of the flask's mantle which has a low resistance to pressure. As a result, the flask does not have an aesthetic shape and the product quality is affected.
It is also known to make a hollow foam body by extrusion blow processing and some additional further processing. A hollow body may be made using only an extrusion blow process--which then becomes a hollow foam body--but in practice, to obtain any shape, in a melt-heating process direct from the extruder, is also required for producing a container for a liquid product, for example for body-care/medicine agents. Another standard process uses a circular or flat half-processed material which process is limited to producing some shapes, such as round or other simple geometrical basic forms. These bodies or, In this case, containers are designed for thermal insulation, for better dimension stability, or for the purpose of coating the container. They are, in part, staple products, such as a jar as described. Their structure has a volume greater than 1 liter and a wall thickness of more than 1.2 mm. however, it is desirable to obtain a low foam density.
In particular, DE-A 15 04 359 discloses that uncontrolled expansion will occur in a trial to achieve a satisfactory low foam density during extrusion blow processing and the wall thickness cannot be regulated. Therefore to overcome this problem, an integrated process to form a solid outer cover and an inner cover is described, which however is limited in its process engineering characteristics and cannot improve the properties of the hollow body, for example the surface or the diffusion-sealing properties. The disadvantage of this process is the length of blowing time required in the extrusion blowing method, which is longer than the normal time usually needed in producing a packaging from the hollow body (DE-A 15 04 359: blowing time=60 seconds).
Foamed containers for packaging are also described. However, they have larger discharge mouths, so that the container coating has no special discharging function, such as deformability and recovery of its initial shape, which must occur for metered delivery of the discharged product. The foamed containers have another disadvantage, namely their surfaces are not smooth. This lessens the acceptability of the product by the consumers.